

A065868


Initial n digits in decimal portion of golden ratio phi (or tau) = (1 + sqrt 5)/2 form a prime number.


0




OFFSET

1,1


COMMENTS

887 certified prime with Primo.
Note: the upper bound of 10^6 in this program has not actually been reached, so the next term may occur at any value >8867.  Ryan Propper, Aug 12 2005
Search limit is 200000.  Serge Batalov, Jun 21 2017


LINKS

Table of n, a(n) for n=1..9.


MATHEMATICA

phi = First@ RealDigits[N[GoldenRatio  1, 10^6 + 1]]; Do[k = FromDigits[Take[phi, n]]; If[PrimeQ[k], Print[n]], {n, 1, 10^6}] (* Ryan Propper, Aug 12 2005, edited by Michael De Vlieger, Jun 21 2017 *)


CROSSREFS

Cf. A047658, A057563, A001622.
Sequence in context: A211891 A060599 A319774 * A144017 A032419 A225163
Adjacent sequences: A065865 A065866 A065867 * A065869 A065870 A065871


KEYWORD

base,nonn


AUTHOR

Jason Earls, Dec 07 2001


EXTENSIONS

a(4)a(6) from Ryan Propper, Aug 12 2005
a(7)a(9) from Serge Batalov, Jun 21 2017


STATUS

approved



